1. Field of the Invention
The invention disclosed herein relates to a disposable carbide cutting blade assembly for a universal rotary cutting head. The assembly of the present invention comprises a disposable carbide blade blank having its cutting surface contoured to the desired configuration, a smooth front, rear, and bottom surface, and a hole extending through the carbide blade blank. The carbide blank is positioned against a steel backer plate, which in turn is provided with a ledge for supporting the carbide blank from below, and a smooth front surface against which the rear surface of the carbide blank rests when properly seated in position. A safety pin protrudes from the front face of the steel backer plate, and extends into the hole within the carbide blank to safely seat the carbide blank against the steel backer plate by eliminating the risk of the carbide blank being ejected from the cutting head during use. The rear surface of the steel backer plate is provided corrugations along its entire height for mating with the corrugations on the inner wall of a slot of a universal rotary cutter head.
2. Description of the Background
The woodworking industry makes use of numerous types of cutter assemblies. The precise contour of the final shaped piece determines the particular tool to be used. Wide varieties of tools have thus been developed, some of which are used for shaping artificial materials or particularly hard woods. The machining of such artificial materials or hard woods has traditionally required the use of very hard cutting tools. However, often such tools have been particularized to a single, specific function, making it a very expensive endeavor to attempt to produce a variety of shapes of hardwood or artificial wood products.
In order to shape artificial wood pieces and hard wood pieces, one such hard tool which woodworkers have used in the past include hard metal or carbide insert blades specifically contoured with the shape of the final piece to be produced. Often times, these carbide blades are held in rotary cutter head assemblies that are specifically dedicated for use with that carbide blade insert. The dedicated carbide insert heads have a circumference which is provided with an identical profile to the cutting profile of the carbide blade insert. Such identical profiling of the cutting head is required in order to fully support the very thin carbide insert, whose thickness is usually only 2 mm. Lacking such support, the thin carbide insert would break immediately upon impact with the surface to be shaped. Thus, the only known prior use of disposable carbide cutting inserts comprised delicately machined cutter heads that were specifically profiled for that one carbide blade insert. Obviously, such dedicated cutter heads required special machining, and resultantly were very expensive to use and to replace. Further, the option of producing a numerous variety of molding designs was vastly limited due to the cost of having a single dedicated cutting head for each desired profile.
One alternative to using such expensive, dedicated cutter head assemblies is to use a universal rotary cutter head, i.e., a head which can accept any self-supporting cutting blade assembly of any shape profile, such as a solid steel blade or a combination of a carbide blade with a steel backer assembly. Unfortunately, such systems require either sharpening or the expensive replacement of the blade after a short usage period. These carbide blade and steel backer assemblies have, in one embodiment, comprised a carbide insert which is brazed or soldered directly onto the steel backer, the combination then being profiled to the desired contour.
This brazed or soldered carbide cutting blade/steel backer plate assembly presents two problems. First, in order to provide the hardened carbide blade assembly with the desired cutting profile, a diamond grinding wheel must be used. As the hard carbide insert is profiled by the diamond grinding wheel, the softer steel backer plate is simultaneously abraded, often times loading up or fouling the abrasive texture of the diamond grinding wheel. Such fouling requires the machine operator to terminate the profiling process, clean the diamond grinding wheel of the excess scrap from the steel backer plate, replace the grinding wheel, and resume the profiling process. Such tedious steps dramatically slow the profiling process, and greatly adds to the cost of producing and replacing the brazed or soldered carbide cutting blade/steel backer plate configuration.
Further, the profiling process itself can be harmful to the carbide cutting blade insert. As the brazed or soldered combination is ground during the profiling process, a large amount of heat is generated which is disproportionately dispersed to the carbide and steel components. As the hard carbide insert heats, it becomes increasingly brittle, thus increasing the risk of fracture of the carbide insert during the profiling process, and in turn increasing the production and replacement cost of the assembly. Such expense prohibits these assemblies from affordably being classifiable as disposable components.
A second embodiment of previously known carbide blade and steel backer assemblies have utilized a carbide cutter plate which is held against a steel backer plate by means of a pressure block from the front and by means of a ridge on the steel backer plate mating with a longitudinal groove on the rear surface of the cutting plate to radially hold the cutting plate in place. The combined carbide cutter plate and steel backer plate could be moved radially to the outside of the cutter body, one corrugation at a time, such that the original cutting diameter could be maintained when the blades were sharpened. During the sharpening procedure, it was not necessary to grind the steel backer plate, such that the difficulties associated with the brazed/soldered embodiment in grinding the combination was overcome. However, this embodiment required the use of a dedicated cutter head to hold the assembly in place during use, and was therefore limited to only a few sharpening profiles. This limitation and the extreme cost associated with this configuration has prohibited its acceptance or wide spread usage in the woodworking industry.
Yet a third embodiment of previously known carbide blade and steel backer assemblies have comprised large carbide cutting blades provided with corrugations on one side for mating with the corrugations on the adjacent, front side of a steel backer plate. The rear side of the steel backer plate is likewise provided with corrugations for mating with the facing corrugations on the interior slot wall of a universal cutter head. Through such a corrugated assembly, the carbide cutting blade may be adjusted radially, while the steel backer plate is held in its original position. Thus, during the re-sharpening procedure, only the carbide blade need be sharpened. However, the initial machining of the carbide blanks to provide them with corrugations for mating with the steel backer is a hazardous and expensive endeavor. Namely, as the carbide blanks are machined with the corrugations, the material expelled comprises minute pieces of carbide which can be inhaled by a machine operator or which may become imbedded in the operator's skin, making such a machining process a significant health hazard. Further, when the carbide cutting blades are sharpened, material must always be removed from the blade surface, which in turn changes the cutter profile of the blade, regardless of the care taken by the machinist.
For example, U.S. Pat. No. 5,658,101 to Hammer describes a milling head having a series of slots for receiving a combination of a backing plate and blade plate, both the backing plate and the blade plate being provided with a series of interacting teeth and grooves which must be specially machined into the hard metal of the blade plate. As explained above, such machining imparts a significant cost to the individual blade plate making it economically infeasible to classify the blade plate as disposable. In fact, the system of Hammer '101 is particularly designed to enable a user to shift the blade plate radially outward for reshaping the blade plate, as the disposal of the specially machined blade plate after the dulling of the cutting surface caused by its initial use would be cost prohibitive. A dowel pin is also provided on the steel backer plate which engages an oblong slot on the blade plate to preclude an axial displacement of the blade plate. The oblong slot is particularly configured to allow and in fact encourage the radial displacement of the blade plate with respect to the support plate in order to allow the blade plate to be extended for sharpening and reuse. Thus, the dowel pin/slot arrangement has no effect on preventing the radial displacement of the blade plate during use, such that the system must rely on the interaction between the teeth on the backer plate and the specially machined grooves on the hard metal blade plate.
U.S. Pat. No. 5,211,516 to Kress et al. likewise describes a rotary boring tool having a reversible knife plate, the knife plate being equipped with a series of specially machined grooves which engage a series of mating teeth on a clamping shoe to form a positively locked connection between the knife plate and the clamping shoe.
U.S. Pat. No. 5,033,916 to Danklau describes a rotatable milling or drilling head holding a plurality of cutting inserts each provided with a series of specially machined indentations for receiving a clamping dog associated with the head which bears against the indentation to hold the cutting inserts in place during operation.
U.S. Pat. No. 3,946,474 to Hahn et al. describes a rotary cutting head having a series of bits helically arranged around the periphery of the cutting head. Each bit comprises a steel holder having a serrated back wall, and a cutting edge made of tungsten or carbide which is permanently affixed to the steel holder, such that replacement of the cutting edge requires replacement of the entire steel holder/cutting edge assembly.
U.S. Pat. No. 3,309,758 to Williams describes a rotary cutting tool having a bit backing optionally provided with serrations on its rear surface which engage complemental serrations on a recessed wall of the cutting tool. An optional eccentrically disposed pin extends from the front of the bit backing to engage a central opening in the cutting bit, the eccentric pin being flexed during installation of the cutting bit to hold the bit in place during use. Optionally, the pin may be eliminated and the cutting bit held against the bit backing using a wedge. Unfortunately, this assembly is entirely impractical for current high speed rotary hard wood shaping applications using a standard carbide cutting blade, as the minimal size of a standard carbide cutting blade requires that a back plate be particularly configured to embrace the entirety of the rear and bottom surfaces of the cutting bit, including providing the upper surface of the back plate with a contour that matches the top surface of the cutting bit, in order to prevent the carbide bit from splintering, cracking, or otherwise being damaged during use.
Each of the above-described embodiments require substantial machining to place the combined carbide cutting surface/backer plate assembly into an operative arrangement and to continue their use, including soldering, machining of grooves, sharpening, etc. Such machining processes provide for greater possibility of error in the fine machining of grooves and aligning of components for welding, and greatly increase the cost of these assemblies, likewise increasing the cost of their replacements and prohibiting them from taking on a disposable character.
It would therefore be advantageous to provide carbide cutting blades for use in a universal cutting head which could be produced at little expense, such that the carbide cutting blades could be used until dulled and then disposed of and readily replaced, while ensuring that the blades are securely fastened within the cutting head body.